These drive models used a similar single density, single side floppy data storage format to that used by the Commodore 1541 drive, but with a slightly different data marker indicating which model originally formatted the disk.
Commodore released a high-speed floppy disk drive for the Plus/4, the Commodore 1551, which offered much better performance than the C64/1541 combination because it used a parallel interface rather than a serial bus.
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Like the 1541 and 1571, the 1581 has an on board MOS Technology 6502 CPU with its own ROM and RAM, and uses a serial version of the IEEE-488 interface.